The goal of this competing renewal is to study the impact of sex work law reform on mitigating or potentiating HIV/STI risks and access to HIV/STI-related care among female SWs. The Canadian government has recently introduced new legislation (Bill C-36) that will criminalize the purchase of sex (clients) and anyone who economically profits from prostitution (e.g., third parties, such brothel managers) while leaving the selling of sex as legal. This approach of criminalizing clients and third parties, but not SWs, often referred to as the Nordic model, has received increasing international attention over the last year, with similar laws/policies introduced in the EU, UK, and a growing number of US cities, despite a complete dearth of research on its intended and unintended impacts. Scientists, health professionals, and community have expressed strong concern that this law will escalate structural HIV/STI risks through heightened stigma and reduced social cohesion among SWs, displacement of SWs to hidden and unsafe venues to avoid police persecution, and increased rates and spatial clustering of violence and homicide. There is also increasing concern that police will use new means to harass and target SWs, including administrative laws (e.g., public nuisance, loitering), drug offenses, and court-mandated drug treatment for SWs who inject drugs (SW-PWIDs), which may further elevate sexual- and drug-related HIV/STI risks. Whether and how these new prostitution laws will affect structural HIV/STI risks and sexual- and drug-related harms for SWs will be important for international and US community and global policy. Through support from an R01, our team has assembled, recruited, and followed a large community-based cohort of street and off-street female SWs across Vancouver since 2005, known as the AESHA cohort (>90% retention). Vancouver is an ideal location for this research for several reasons: the imminent policy reform opportunity; site of one of the only longitudinal cohorts of SWs in North America; progressive harm reduction programs (e.g., supervised injection facilities) for SW- PWID; site of government-sponsored `seek, test, treat and retain' HIV efforts; and universal health coverage that allows us to link survey and biological data with administrative databases, permitting assessment of health care barriers free of the confounding effects of medical health insurance. Given the large number of countries, as well as US cities, contemplating legislative reform around sex work in the absence of empirical data, this study allows an unprecedented opportunity to evaluate a structural intervention of sex work law reform as a naturally-occurring experiment on HIV/STI risks and other health outcomes among SWs. The evaluation of structural interventions is rare and a high priority in the 2014 Trans-NIH Plan for HIV Research.